1. Field of the Invention
The present invention generally relates to a semiconductor element and a manufacturing method thereof and, more particularly, to a semiconductor element having a bonding par or a bump pad or a probing pad that serves as a connection terminal of the semiconductor element in a semiconductor device and a manufacturing method of such a semiconductor element.
2. Description of the Related Art
Generally, a semiconductor element incorporated in a semiconductor device is provided with a plurality of electrodes for acquiring an electric contact with an external device. For example, if the electrodes serve as connection pads of bonding wires, those electrodes are referred to as bonding pads. If the electrodes serve as connection pads of bumps, those electrodes are referred to as bump pads. Additionally, if the electrodes serve aw connection pads for contacting with probe needles, those electrodes are referred to as probing pads. Hereinafter, the bonding pads are explained below as a representative of the bonding pads, the bump pads and the probing pads.
FIG. 1 is a perspective view showing a part of an integrated circuit package (semiconductor device) in which a semiconductor element having a plurality of bonding pads are incorporated. As shown in FIG. 1, the bonding pads 6a of the semiconductor element 6 mounted on a die stage 4 of a lead frame 2 within the semiconductor device are connected to inner leads 2a of the lead frame 2 by bonding wires 8.
FIG. 2 is a plan view of the bonding pads shown in FIG. 1. FIG. 3 is a cross-sectional view taken along a line III-III in FIG. 2.
As shown in FIG. 2 and FIG. 3, generally, the bonding pads 6a formed in the semiconductor element have a structure in which many conductive plugs 16, which are made of tungsten or the like and arranged in a matrix pattern, are formed on a lower wiring layer 14 made of aluminum or the like, and an upper conductive layer 18 made of aluminum or the like is formed on the conductive plugs 16. Between the lower wiring layer 14 and the upper conductive layer 18, an insulating layer 20 is formed around the conductive plug 16.
It should be noted that the lower wiring layer 14 is formed on an interlayer insulating film 12 formed on a semiconductor substrate 10, and serves as an internal wiring of the semiconductor element. Additionally, an outer circumferential portion of the upper conductive layer 18 is covered by a cover film 22, and the upper conductive layer 18 is exposed in openings formed in the cover film 22.
Here, in a process of forming the semiconductor element, for example, an electric characteristic test is performed by performing an electric test so as to determine whether or not the semiconductor device is good or defective. In this case, is it necessary to bring test probe pins into contact with the bonding pads 6a (upper conductive layer 18). When the test probe pins are pressed onto the upper conductive layer 18, a stress is concentrated into the insulating layer, which is hard and brittle as compared to the upper aluminum layer and the conductive plugs 16. Due to the stress concentration, there may be a case in which a crack is generated in the insulating layer 20 between the conductive plugs 16.
Such a crack does not propagate to the conductive plug 16, and ends when the crack reaches the conductive plug 16. However, the conductive plugs 16 are arranged in a matrix pattern, and in the cross-section shown in FIG. 4, the crack may propagate within the insulating layer 20 without running into the conductive plugs 16.
Moreover, a flaw may be formed on the upper conductive layer 18 by the test probe pins being pressed onto the upper conductive layer 18. Such a flaw may propagate within the insulating layer 20. Then, if a water component enters the flaw, the water component enters inside the semiconductor element, which may cause a moisture resistance defect.
Thus, in order to solve the above-mentioned problem, there is suggested a bonding pad having a structure in which the conductive plugs and the portions of the insulating layer are exchanged so as to make a grid-like conductive portion 16A and island-like insulating layer 20 as shown in FIG. 5 and FIG. 6 (for example, refer to Patent Document 1). It should be noted that FIG. 5 is a plane view of the bonding pad 6Aa having the grid-like conductive portion 16A, and FIG. 6 is a cross-sectional view taken along a line VI-VI of FIG. 5.
That is, between the upper conductive layer 18 and the lower wiring layer 14, the grid-like conductive portion 16A corresponding to the conductive plugs is formed of tungsten or the like, and an insulating material is filled in each square portion within the grid-like conductive portion 16A so as to form the insulating layer 20. According to such a structure, the insulating layer 20, which tends to generate a crack, is surrounded by wall surfaces of the grid-like conductive portion 16A. Accordingly, is a crack is generated in the insulating layer 20 corresponding to one square portion, the crack does not propagate to the insulating layer 20 of other square portions or the insulating layer 20 outside the grid-like conductive portion 16A.
The following documents relate to the above-mentioned background art of the present invention.
Patent Document 1: Japanese Laid-Open Patent Application No. 2002-208610
Patent Document 2: Japanese Laid-Open Patent Application No. 10-64945
The above-mentioned grid-like conductive portion 16A can be formed by forming portions corresponding to openings of the grid pattern (that is, the island-like insulating layer 20) and filling tungsten or the like between the island-like insulating layer 20. However, since the insulating material forming the insulating layer 20 has a pole shape, a contact area with the lower wiring layer 14 is small. Thus, there may be a problem in that the pole-like insulating layer 20 separate and fall off from the lower wiring layer 14 as shown in FIG. 7 when performing etching, ashing, post processing, cleaning, and drying in the forming process of the insulating layer 20 or when performing cleaning or drying in a subsequent process. It should be noted that, in FIG. 7, the island like insulating layer 20 is indicated not as a square pole but a cylindrical pole. Although the island-like insulating layer 20 is indicated as a square pole in FIG. 4 and FIG. 5, it may be a shape close to cylindrical pole when forming in practice.
In addition, the may happen a problem in that the conductive material cannot be properly filled in a portion indicated by a reference numeral 38 in FIG. 8 or a recess is formed when filling the conductive material such as tungsten or the like around the island-like insulating layer 20, which cannot acquire a good coverage. It should be noted that the island-like insulating layer 20 is indicated as a cylindrical pole also in FIG. 8.